Add support for travis-ci/fix tests for older versions of django.

With this diff, all that should need to be done to add travis-ci is:
- log into https://travis-ci.org with github, and
- flip the switch!

![image](https://f.cloud.github.com/assets/767671/559556/385147d4-c452-11e2-9eb9-6b5341db75de.png)